Too Many Cables!
I like cords and cables as much as the next guy (or gal) but there is a limit! A could years ago I picked up some Chauvet Slimpar 56 LED light fixtures because I was tired of hauling around heavy standard bulb fixtures for the band I played in. The LED units had some huge advantages, low power, lightweight, etc… but I found out quickly that for every one of them there were TWO cords (power and DMX control) that needed to be strung and plugged in, whereas in the past a light had only ONE cord to deal with. So it didn’t take long for me to start investigating ways to make the whole business “cable free”. This is what I ended up with:
It is basically a standard LED par 56 fixture mounted on top of an enclosure that houses a 12v AGM battery and wireless DMX board.
There are a few battery powered wireless DMX fixtures out there on the market currently, but I’m astounded at how expensive they are. Here are a couple of examples:
This one for $499
This one (which is not wireless DMX only battery) for $160 –
This one for $200 –
The first and third examples both require proprietary “D-Fi” USB transmitters to be purchased for about $30 each – so you can add that onto the cost.
The total cost of the unit I built was more in the $100 range per fixture. The retail cost of a Slimpar 56 is around $70 (on sale) and you can get similar Chinese fixtures for one quarter that cost on ebay! (lot of 4 for $80 – $20 each!) Here is a cost breakdown:
So I figured that I could build them for between $100 and $300 less than I could buy them for. Put another way: for what I would spend to buy 4 lights, I could build and have 8 to 16 lights. I thought it was worth the effort.
A quick note before I detail the construction steps – one of the parts, the 12V to 5V converter unit.. I realized later that I could have just as easily used a little 5V regulator IC (LM7805) that would have cost 20 cents rather than $5.50… That would have saved quite a bit. I didn’t realize or consider that the little wireless DMX board needed so little power that I could have use the 5v chip even without a heatsink. Oh well… live and learn.
Here are the parts that I used. I’ve linked most of them to ebay searches because in most cases I don’t know if the auction that I used will still exist when you read this.
|Par Fixture ether Chauvet or Chinese import|
|12V 4.5Ah AGM Battery|
|Wireless DMX Board|
|5.5mm x 2.1mm Metal DC Jack Female|
|Nylon Hex M3 Spacers Screw Nut Standoffs|
|DC-DC Converter 12V Step Down to 5V|
|Pair of PVC 4×4 end caps|
|4×4 PVC post sleeve|
|3-6.5mm Cable Waterproof PG7 Plastic Gland|
|Aviation Plug Male & Female 16mm 4 pin GX16-4|
|Misc Wire (one 2 conductor for power and one 3 conductor for DMX) Local Hardware Store AND Misc Hardware (bolt, washers, wingnut) Local Hardware Store|
|Female XLR Connector – I forgot this on the cost list above – it raises the cost about $2. 🙂|
Building the Base
Most of this build is copied from someone else’s battery powered LED fixture project I saw, and for the life of me I can’t remember where I saw it. It was somewhere out there on the inter-web. But anyhow, they used 4×4 PVC post sleeve material as a housing, and I like the idea and stuck with it. It is probably best to buy the sleeve from a local hardware store because the shipping on the sleeve is kind of high. And while you are there, pick up the end caps and make sure that the caps fit tight on the sleeve. I gave them a gentle sanding so that paint would hold better and shot a code of matte black onto the sleeves and caps. They look something like this:
In the photos above you can see that I’d already drilled the holes and installed some of the parts. The first set I made of these units, I made the base about 7.5 inches – just beyond the length of the par fixture brackets. But the next set I cut a little shorter, more like 6″. I found that the best way to cut the PVC into lengths was to use a bandsaw. Any fine toothed hand saw would work as well. I would avoid using a circular saw of any time. PVC tends to pinch and become an instant projectile with those saws. Kind of dangerous. Be careful!
You can see of the photos that there are quite a few holes, around 11 total. For the bolt that will hold the fixture to the PVC housing, I used 3/8″ size, about 2.5″ long. In order to keep things as rigid as possible I used LOTS of large ‘fender washers’. One washer on either side of the PVC shell to keep it from wobbling – I squeezed them as tight together as I could with a 3/8″ nut… then on top of that nut (on the outside of the housing) I put another large washer for the fixture bracket to rest on… then the bracket.. then another washer, slightly smaller, and then finally a wingnut used fasten the fixture to the whole thing.
Note that until the AGM battery is put into the housing, the whole thing will be VERY tippy if you try to attached the light fixture. There battery has quite a bit of weight and it is that weight that gives the base its stability. So don’t bother attaching the light until the very end.
I offset the hole for the fixture holding bolt as far to the edge of the sleeve as I could and still have room for the fender washers so that there would be room to mount the other items on the top.
You’ll need to drill 6 small holes for the wireless DMX board. 2 of the holes are to access the pushbutton settings switch and to view the status LED. The other four holes are for the nylon standoffs that will hold the board in place. Getting the hole placement right is pretty tricky. I put one of the DMX boards on my scanner, scanned it, printed it actual size and then used that printout as a template to mark off where to drill the holes.
Beyond that, you’ll need 4 more holes:
1 hole for the wireless DMX antenna
1 hole of the power switch
1 hole for the 12v charging jack
1 hole for the cable strain relief
They can all be arranged on the opposite side of the PVC sleeve from the fixture holding bolt.
Modifying the Fixture
There is a good chance that the LED fixture you have does not happen to have a DC input jack. This is, of course a very important thing to work through before you even start this project! Most all of the LED par fixtures I have seen use a 12V switching power supply inside the case to step the 110V AC power input down to 12V DC. That is actually a pretty convenient thing because it is super easy to tap in a 12V input jack. The first slim-par units I bought had the 12V input already built in. The newer units did away with that connector to save a little money I would imagine.
On the photo above you can see the little 4 pin connector on the lower right just below the AC outlet which I added. It is pretty simple to do. Take the light apart.
Drill a hole for the connector and mount it in:
You’ll want to solder the wires onto the connector BEFORE you mount it – it is easier that way. Then find the switching power supply board. It will be the board that is (electrically) between the 110V AC input and the rest of the fixture. You’ll have to unscrew that circuit board and find the 12V output wires. Make sure to check the voltage output with a voltmeter. BE CAREFUL!! Switching power supplies can be very dangerous – they use high voltages!! (in the thousands of volts range!) Once you are sure that you have found the 12V output connection – you can solder your wires in parallel with the existing connections.
Fasten the board back into the fixture and put the whole thing back together.
If there is any doubt about “hackability” of a particular fixture – you might want to just order up a single fixture to see if you can make the needed modifications – and once you are sure that you are able to use a 12V DC battery supply with the given fixture, then order up a batch of them.
Now back to working on the base…
We can turn our attention back to wiring up the “Guts” of the unit – all the stuff in the base.
Here I have all the stuff laid out that I’ll use:
I start by soldering the XLR connectors onto the 3 wire cable and the 2 wire DC supply wires onto the 4pin “aviation” plug. This is a reference diagram for the 3pin XLR DMX wiring:
The aviation plug can be wired any way you like… just make sure that the +12v and Ground pins match up with how you wired the plug you retrofitted into the PAR fixture! I used pins 1 and 2, pin 1 for +12v and pin 2 for ground.
This is the wiring diagram I ended up with for all of the “innards”:
After I had the power cable and the DMX cable soldered and threaded through the strain relief I set those bases aside.
Next I set to work soldering the switch to the DC charging jack.
Notice that I didn’t always pay too much attention to making the wires the proper colors. Normally the wire from the center conductor of the switch above would be RED for + voltage. In this case I just used a bit of black wire.
Next I soldered the 12v to 5v DC converter into the circuit:
Usually after soldering the wires together I wrapped them with a bit of electrical tape for protection. I would strongly suggest that you use 3M brand electrical tape – it make a big difference.
Next I can solder the pigtail wires from the DMX board into the mix and mount all those parts inside the base.
Fitting the battery and the DC converter in is a pretty tight fit:
But it kind of keeps everything from moving around that way. You can see from the above picture that the PVC sleeve bulges out a bit from the battery, but here again, that keeps the end cap fit very snug. I’ve had dozens of gigs with the end caps just press fit on and because they fit so tight, they never fell off.
Having soldered up all the wires, mounted the board, switches, jacks, battery, in the housing, I set the aside and get ready to assemble the fixtures and put on the finishing touches.
Playing with Homemade Sugru
Even the right angle XLR connectors that are available, I felt, stuck out too far from the back of the light fixtures and so I opted to get inexpensive XLR connectors, solder the wire to the connectors and throw away the XLR connector sleeves. To protect the wires on the back of the connectors there is a product called “Sugru” that would be perfect, but being cheap, I found several sites that showed how to make it yourself!
It is basically cornstarch and silicone caulk mixed together to a “play-dough” consistency.
I took a little bit and molded it around the wire and bare connector:
In the photo above you can see one of the bare connectors and one that I molded with my homemade sugru. After curing for an evening it hardens up to a more stuff rubber consistency – perfect for protecting the wires – and the result is that the entire connector fits snugly into the socket and is protected.
So this is what it finally looks like:
And I’m very happy with how they work.
At first I used 7 Amp Hour batteries, but they lasted so long, more than 10 four hour gigs, so with the second batch of lights I made, I used 4.5 Amp Hour battery which were a little lighter and still lasted a very long time.
I charge them up with something like this:
I also made a foot controlled Raspberry Pi DMX light controller. I’ll try to post the info on how I made that as well.
Thanks for checking this out!